K. Yamanaka et al., FLUCTUATION FIELDS AND MEDIUM NOISE IN COCRTA AND COCRPT FILMS, Journal of magnetism and magnetic materials, 152(3), 1996, pp. 411-416
The correlation between magnetic viscosity and medium noise in CoCrTa
and CoCrPt longitudinal thin-film media was investigated by measuring
the time dependence of the remanence coercivity H-r and the read/write
characteristics. The media were prepared by de magnetron sputtering u
nder various conditions. Fluctuation fields H-f of the magnetic viscos
ity at H/H-r=1 were obtained from the slopes of the H-r versus In t pl
ots. The medium noise decreases with kT/H-f (the product of activation
volume and saturation magnetization per unit volume), and is independ
ent of other magnetic properties, such as the coercivity and the reman
ent magnetization per unit area. The medium noise thus primarily depen
ds on the size of the minimum unit of the magnetic moment in reversal.